Precision feed for machine tools



May 18, 1965 R. E. PRICE ETAL 3,183,631

PRECISION FEED FOR MACHINE TOOLS Filed Feb. 21, 1963 6 Sheets-Sheet 1 INVENTORS RALPH E. PRICE F BY CHARLES E. TOLBERT ATTORNEY May 18, 1965 R. E. PRICE ETAL 1 PRECISION FEED FOR MACHINE TOOLS Filed Feb. 21, 1963 6 Sheets-Sheet 2 NVENTORS RALPH 5. PRICE BY CHARLES E. TOLBERT ATTORNEY May 18, 1965 R. E. PRICE ETAL LFRECFSION FEED FOR MACHINE TOOLS 6 Sheets-Sheet 3 Filed Feb. 21, 1.955

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May 18, 1965 R. E. PRICE ETAL 3,183,631

PRECISION FEED FOR MACHINE TOOLS Filed Feb. 21, 1963 6 Sheets-Sheet 4 INVE'lNTOR RALPH E- PP/CE BY CHARLES E. TDLBERT TI'ORN EY y 8,1965 R. E. PRVICE ETAL 3,183,631

PRECISION FEED FOR MACHINE TOOLS Filed Feb. 21, 1963 6 Sheets-Sheet 5 INVENTORS RALPH E. PRICE CHARL 6 E- TDLBERT ATI'ORNEY R. E. PRICE ETAL 3,183,631

PRECISION FEED FOR MACHINE TOOLS 6 Sheets-Sheet 6 May 18, 1965 Filed Feb. 21, 1963 INVENTORS RALPH E. PRICE BY C HARLES E-TOLBERT TI'QRNEY L Ill! Hllll United States Patent This invention relates to feed mechanisms for a machine tool, especially grinding machines, and more particularly, to means for effecting relatively small movements of a grinding wheel support at the end of a grinding operation.

In present day grinding, a workpiece is ground within limits of tolerances which are expressed in millionths of an inch. With present day feed mechanisms and grinding wheel support mountings, it is difficult to accurately. move a wheel support even .0001".

' When a driving force is applied to a grinding wheel support, it mustbe great enough to overcome starting friction and inertia. Once these forces have been overcome, a much lesser force is suflicient to keep the support moving. It is not possible to change from the starting force to the running force without moving the support too fast and too far. What happens is that a strain is built up in the feed mechanism until it is equal to or greater than the required starting force. When the starting resistance has been overcome, the starting force continues until the strain is releasedwith the result that a support is'advanced abruptly with the risk of damage to the workpiece. Furthermore, after the feed mechanism stops, the strain is relieved and causes the wheel support to continue to move or drift. This movement may be prevented byrneans of a pressure operated device by which the relief of strain may be controlled.

It is, therefore, an object of. the present invention to provide means to control the release of strain in the feed mechanism of a grinding machine. a

Another object is to provide an adjustable resistance to the release of strain in a feed mechanism.

Another object is to provide means whereby a more or less conventional feed mechanism can be made to adjust a grinding wheel support by increments of .0001 or less.

Another object is to provide means for adjusting a wheel support feed mechanism while said wheel support is held against movement by a' fluid pressure device, and bleeding said fluid pressure device to permit movement of said wheel support in response to adjustment of the feed mechanism until the desired adjustment is shown on an indicator in the path of said wheel support.

FIG. 1 is a front elevation of a centerless grinding machine.

FIG. 2 is a left hand end elevation, partly in section, taken on line 22 of FIG. 3, showing details of the wheel feed mechanism. 7

FIG. 3 is a partial front elevation, partly in section, taken on line 3-3 of FIG;- 5, showing the feed mechanism.

FIG. 4'is a diagrammatic'sketch of a wheel feed mechanism with hydraulic control elements for effecting rela-' tively small incrementsof movement of a wheel support.

FIG. 5 is a partial right hand end elevation, partly in section, taken on line 55 of FIG. 3, showing the connections between the feed screw and ratchet mechanism. FIG. 6 is a right hand end elevation of-the feed mecha-' nism.

For illustrative purposes, the invention is shown as applied to a wheel support of a centerless grinder to which the feed mechanism is applied. In some center less grinders, the feed is applied to the grinding wheel support, and others, to the control wheel support. The

invention may also be applied to feed mechanisms of center-type machines.

Grinding wheel support 11 is slidably mounted on bed 10 of a centerless grinder. Grinding wheel 12 is rotatably mounted on wheel support 11. Control wheel 15 is rotatably mounted on control wheel support 16. Workpiece W is supported between wheels 12 and 15 on work rest blade mounted on base 21 on bed 10.

The means for feeding wheel support 11 toward and away from workpiece W consists of a feed screw 3t) rotatably and'slidably mounted in bed 10, and having a piston 31 mounted thereon which is reciprocable in noid 82 is energized, shifting valve 83 to the right and. directing fluid under pressure from line 84 at a pressure cylinder 32. Feed screw 30 is connected to wheel support 11 through vertical shaft 35 having a worm Wheel 36 at the lower end in operative engagement with the threads of feed screw 30. The upper end of shaft 35 has a worm Wheel 40 connected through suitable gearing to feed hand wheel 45. Hand wheel may be actuated manually or by power to rotate shaft 35 and move wheel support 11 relative to feed screw 39 and bed 10.

' Power means for rotating hand wheel 45 consists of piston in cylinder 51. Piston 50 is connected through piston rod 52 which has rack teeth 53 in engagement with pinion 54 which, in turn, engages pinion 55 on hand wheel 45. Adjusting screw provides for fine adjustment of hand wheel 45 and the associated feed mechanism.

Means is provided for stopping or preventing the advance movement of wheel support 11. The means consists of a cylinder in Wheel support 11, piston 71 in cylinder 7t and a positive stop 72 on bed 10 in the path of piston 71. The end of cylinder '70 opposite the positive stop 72, is connected to a hydraulic system arranged to supply fluid under pressure to cylinder 70 to stop or prevent the advance movement of wheel support 11, to

retract wheel support 11 or to advance said wheel support 11 at a controlled rate.

The feed mechanism may also be adjusted by turning feed screw 30. The means for turning feed screw 34) consists of a worm gear 105 attached to feed screw 30 and inoperative engagement with worm 106 at one end of shaft 107. At the other end of shaft 107 is a worm gear 108 in operative engagement with worm 109 rotatably supported in housing 110. Worm 199 is mounted on shaft 115 having a ratchet wheel 116, a feed advance pawl 117 and a feed retract pawl 118. Pawl 117 is actuated by fluid motor 120. Pawl1 18 is actuated by fluid motor 121.

Operation Grinding wheel support 11 is advanced for a grinding operation by introducing fluidunder pressure to the right hand end of cylinder 32, shifting feed screw 30, vertical shaft 35 and wheel support 11 to the left until feedscrew 30 reaches the end of its movement.

. Fluid'is then directed to the right hand end of cylin der 51, shifting piston 50 and piston rod 52 to the left to rotate hand wheel 45 and associated feed mechanism including shaft 35 to further advance wheel support 11 after grinding wheel 12 has engaged the work. In order to move wheel-support 11 by piston 50, a strain is introduced into the feed mechanism.

"When the grinding operation .has proceeded to the point where cam 36 engages the feed completion limit switch 81 and piston 71 engages positive stop '72, soledeterminedby relief valve through line 86 to valve 90. 'Valve is held in left hand position by spring 91 and directs fluid under pressure fromline 86 to cylinder.

"70 at the pressure of relief valve 85 to prevent further movement of wheel support 11. By thus stopping wheel Patented May 18, 1965 a support 11, additional strain is introduced into the feed mechanism.

The grinding operation proceeds without feed and performs a-sparkout or round-out operation in the case of plunge grind in a center-type machinein response to relief of strain in the workpiece.

In a centerless machine, arranged with through feed grinding, the wheel in thisposition is set for grinding a series of workpieces to a predetermined size.

When a post process gauge (not shown) shows that workpieces are not being ground to size, the operator shifts valve 100 to the right, connecting cylinder 70 with exhaust for a brief period and allowingwheel support 11 to advance in response to the strain in the feed mechanism by an amount sufficient to cause workpiecesto be ground to a predetermined size.

The amount of oversize is indicated by the post process gauge (not shown) and wheel support 11 may advance a corresponding amount, as shown by indicator 130.

suitably positioned to show the movement of wheel support 11.

If, due to unusual circumstances, the post process gauge (not shown) shows that the work is being ground undersize, the operator may shift valve '90. to the right against spring 91 and connect cylinder 70 with higher pressure determined by the setting of relief valve 92. In response to this pressure, cylinderltl and wheel support 11 will move to the .right until indicator 130 shows that wheel support 11 has been retracted by the amount of,

undersize shown by the post process gauge (not shown);

If, after wheel support 11 has been advanced, the ad? vance has not been sufficient to correct the'error shown by the post process gauge (not shown), additional strain can be introduced into the feed mechanism by further rotation of hand wheel 45 either direct or through ad justing screw 60, or by rotation of feed screw by ratchet wheel 116 and either of pawls 117 or 118; Dar-1 I ing .this adjusting operation,,valves 90 and 109 are in the normal position shown and'valve solenoid 82 -;is energized so that low pressure fluid is applied to piston 71 to prevent further advance of wheel support 11 until, the

additionof strain in the feed mechanism is completed. Valve 190 is again shifted momentarily to theright to connect cylinder 70 briefly with exhaust to permit fur-- ther advance of wheel support 11 in of the strain in the feed mechanism.

We claim:

1. .In afeed control mechanism for a machine tool having a bed, atool support slidably mounted on said bed, a work support, a cutting tool mounted on said tool support, feeding means for advancing and retracting said tool support relative to said work support including a feed screw, a piston and cylinder attached to-said tool response to relief support, a positive stop in the path of said .piston, a

supply of fiuidunder pressure connected to said'cylinder,

meansv to advance said feeding means while said tool sup! port is'held against movement by said positive stop and v the pressure in said cylinder, and means to connect said cylinder with a lower pressure.

2, In a feed controlmechanisrn for a machine tool having a bed, a tool support slidably mounted on said I a piston and cylinder attached to said. wheel support,

means to maintain pressure in said cylinder sufiicient to stop'or prevent movement ofsaid wheel support, and

means to changethe pressure-in said cylinder to effect adjustment of said wheel supportin either direction.

4. A grinding machine comprising a bed, a grinding wheel support slidably mounted on said bed, a work support, a grinding wheel rotatably mounted on said wheel support, feeding means for advancing and'retract ing said wheelsupport relative to a workpiece, means to stop the movement of said wheel support comprising a piston and cylinder attached to said wheel support, means to maintain pressure in said cylinder suflicient to stoporprevent movement of said wheel' support, means to change the pressure in said cylinder to effect adjustment of said wheel support in either direction, and an indicator on said bed in the path of said wheel support to show the amount of said adjustment.

5. A grinding machine comprising a bed, a grinding wheel support" slidably mounted on said bed, a work support, a grinding wheel rotatably mounted on said wheel support, feeding means for advancing and retracting said wheel support relative to a workpiece, means to stop the movement of said wheel support comprising a piston and cylinder attached to said wheel support and operable when said piston engages a positive stop to retard or stop the movement of said wheel'support, an indicator in the path of said wheel support and operable'to show fine increments of movement of said wheel support, a supply of fluid under pressure connected. to said cylinder, means to adjustsaid wheel support in eitherdirection comprising a valve apparatus operable to reduce the pres sure .in said cylinder until .said indicator shows the desired movement of said wheel support in one direction and also operable to increase the pressure in said cylinsupply of fluidunder pressure'connected to said cylinder,

means to advance said feeding meansywhile said tool support is held against movement by said positive stop and the pressure in said cylinder, a valve in said fluid supply normally .in position to connect said. cylinder with exhaust, means actuated by said feeding means to shift said valve toconnect said cylinder with pressure .to stop said wheel support, means tolconnect said cylinder bed, a work support, a cutting tool-mounted' on said tool support, feeding .means'for advancing and retractingsaid tool'support relative to said work support including 1* a feed screw, a piston and cylinder attached to. said tool support, a positive stop in the path of said piston, a supply,

of fluid under pressure connected to said cylinder, means to advance said feeding means while said tool support while said cylinder is connected to said lowerpressure. 3. A-grinding machine gomprising a bed, a grinding when support. slidably mounted on said bed, a work is held against movement by said positive stop and-the pressure in said cylinder, means to connect said cylinder with a lower pressure, and an indicator in-the path, or.

said-tool support to show movement of saidtool support with a lower. pressure and an indicator 'in the path of said tool support and graduated 'to showhrovement of saidtool support while said cylinderis connected'to said lowerpressure;

7; A'grindingima'chine having a bed, a grinding wheel support slidably mounted on said bed, a work support,

a grinding wheel rotatably'mounted on said wheel'support, manually operable feedingimeans for advancing and retracting said wheelsupport relative to a workpiece, a piston andcylinder attached to said wheel support, a positive stop inthe path of said piston,- asupply' of fluid underpressure high enough v,to. prevent movement of said piston :in said'cylindengmans to. advance said feeding means an amount in excess of thelde'sired movement of said'wheelisupportwhile said piston prevents movement of said wheel; support, .an indicator' imthe path of said wheel support, means to prevent movement of said wheel support or to adjust said wheel support in either direction until said indicator shows the desired movement comprising means to control the pressure in said cylinder.

8. A grinding machine having a bed, a grinding wheel support slidably mounted on said bed, a work support, a grinding wheel rotatably mounted on said wheel support, manually operable feeding means for advancing and retracting said wheel support relative to a workpiece, a piston and cylinder attached to said wheel support, a positive stop in the path of said piston, a supply of fluid under pressure high enough to prevent movement of said piston in said cylinder, means to advance said feeding means an amount in excess of the desired move ment of said wheel support while said piston prevents movement of said wheel support, an indicator in the path of said wheel support, a valve operable in one position to permit exhaust of fluid from said cylinder and in the other position to prevent exhaust of fluid from said cylinder, and a second valve operable in one position to supply fluid under pressure to said cylinder high enough to stop movement of said wheel support and in the other position to supply fluid under a higher pressure to retract said wheel support.

9. A grinding machine having a bed, a grinding wheel support slidably mounted on said bed, a work support, a grinding wheel rotatably mounted on said wheel support, manually operable fedeing means for advancing and retracting said wheel support relative to a workpiece, a piston and cylinder attached to said wheel support, a positive stop in the path of said piston, a supply of fluid under pressure high enough to prevent movement of said piston in said cylinder, means to advance said feeding means an amount in excess of the desired movement of said wheel support while said piston prevents movement of said wheel support, an indicator in the path of said wheel support, means to prevent movement of said wheel support or to adjust said wheel support in either direction until said indicator shows the desired movement, and means to advance said wheel support comprising means to reduce the pressure in said cylinder until said indicator shows the desired movement.

10. In a feed control mechanism for a machine tool having a bed, a tool support slidably mounted on said bed, a work support, a cutting tool mounted on said tool support, feeding means for advancing and retracting said tool support relative to said work support, a piston and cylinder attached to said tool support, a positive stop in the path of said piston, a supply of fluid under pressure connected to said cylinder, an indicator in the path of said tool support and graduated to show movement of said tool support, means to effect adjustments of said feeding means and said tool support while said piston is held against said positive stop, said adjustments being in a direction to correct any variations in size of a workpiece, the amount of said adjustments being at least the amount of said variations, and a valve operable to change the pressure in said cylinder to permit said feeding means to move said tool support until said indicator shows that the correction has been completed.

11. In a feed control mechanism for a machine tool having a bed, a tool support slidably mounted on said bed, a work support, a cutting tool mounted on said tool support, feeding means for advancing and retracting said tool support relative to said work support, a piston and cylinder attached to said tool support, a positive stop in the path of said piston, a supply of fluid under pressure connected to said cylinder, an indicator in the path of said tool support and graduated to show movement 6 of said tool support, means to efifect adjustments of said feeding means and said tool support while said piston is held against said positive stop, said adjustments being in a direction to correct any variations in size of a workpiece, the amount of said adjustments being at least the amount of said variations, a valve operable to connect said cylinder alternately with pressure and exhaust, and

x a second valve operable to connect said pressure connection alternately with high and low pressure fluid supplies.

12. In a feed control mechanism for a machine tool having a bed, a tool support slidably mounted on said bed, a work support, a cutting tool mounted on said tool support, feeding means for advancing and retracting said tool support relative to said work support, a piston and cylinder adapted tobe moved relative to one another by movement of said tool support, a positive stop in the path of said piston, a supply of fluid under pressure connected to said cylinder, means to actuate said feeding means while said tool support is held against movement by the pressure in said cylinder, and means to connect said cylinder with a lower pressure.

13. A grinding machine having a bed, a grinding wheel support slidably mounted on said bed, a work support, a grinding wheel rotatably mounted on said wheel support, manually operable feeding means for advancing and retracting said wheel support relative to a workpiece, a piston and cylinder attached to said wheel support, a positive stop in the path of said piston, a supply of fluid under pressure high enough to prevent movement of said piston in said cylinder, means to advance said feeding means an amount in excess of the desired movement of said wheel support while said piston prevents movement of said wheel support, a valve operable in one position to permit exhaust of fluid from said cylinder and in the other position to prevent exhaust of fluid from said cylinder, and a second valve operable in one position to supply fluid under pressure to said cylinder high enough to stop movement of said wheel support and in the other position to supply fluid under a higher pressure to retract said wheel support.

14. In a feed control mechanism for a machine tool having a bed, a tool support slidably mounted on said bed, a work support, a cutting tool mounted on said tool support, feeding means for advancing and retracting said tool support relative to said work support, a piston and cylinder attached to said tool support, a positive stop in the path of said piston, a supply of fluid under pressure connected to said cylinder, means to effect adjustments of said feeding means and said tool support while said piston is held against said positive stop, said adjustments being in a direction to correct any variations in size of a workpiece, the amount of said adjustments being at least the amount of said variations, a valve operable to connect said cylinder alternately with pressure and exhaust, and a second valve operable to connect said pressure connection alternately with high and low pressure fluid supplies.

References Cited by the Examiner UNITED STATES PATENTS 4/28 Knowles 51l65 8/43 Kullman et al. 51-165 LESTER M. SWINGLE, Primary Examiner. 

1. IN A FEED CONTROL MECHANISM FOR A MACHINE TOOL HAVING A BED, A TOOL SUPPORT SLIDABLY MOUNTED ON SAID BED, A WORK SUPPORT, A CUTTING TOOL MOUNTED ON SAID TOOL SUPPORT, FEEDING MEANS FOR ADVANCING AND RETRACTING SAID TOOL SUPPORT RELATIVE TO SAID WORK SUPPORT INCLUDING A FEED SCREW, A PISTON AND CYLINDER ATTACHED TO SAID TOOL SUPPORT, A POSITIVE STOP IN THE PATH OF SAID PISTON, A SUPPLY OF FLUID UNDER PRESSURE CONNECTED TO SAID CYLINDER, MEANS TO ADVANCE SAID FEEDING MEANS WHILE SAID TOOL SUPPORT IS HELD AGAINST MOVEMENT BY SAID POSITIVE STOP AND 